How would I go about saving a JSON file from a webservice to a local JSON file?

Question

I'm currently populating a UITableView with JSON data (NSArray format) from a remote webservice. I would like to speed up the application by making a call to the webservice and storing the JSON data to a local file.

also, is this a good way to do this so the user doesn't have to keep downloading data all the time?

What I'm stuck on is how to save the remote JSON file to a local file. In my -(void)saveJsonWithData:(NSData *)data method how do I save the remote data.

Here's the code I'm using so far (from some Stackoverflow searching)

-(void)saveJsonWithData:(NSData *)data{

 NSString *jsonPath=[[NSSearchPathForDirectoriesInDomains(NSUserDirectory, NSUserDomainMask, YES) objectAtIndex:0] stringByAppendingFormat:@"/data.json"];

 [data writeToFile:jsonPath atomically:YES];

}

-(NSData *)getSavedJsonData{
    NSString *jsonPath=[[NSSearchPathForDirectoriesInDomains(NSUserDirectory, NSUserDomainMask, YES) objectAtIndex:0] stringByAppendingFormat:@"/data.json"];

    return [NSData dataWithContentsOfFile:jsonPath]
}

Then call the function as

- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{

    [self saveJsonWithData:data];
}

thanks for help

score 1 · Answer 1 · answered Sep 05 '13 at 09:29

1

On iOS you should be using NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) to get the document directory. There is no user directory.

answered Sep 05 '13 at 09:29

Wain

118,658
15
128
151

thanks! but do you know how I would save the json from an NSURL to a local json file? – user2588945 Sep 05 '13 at 09:40
Your method will save the data. I assume you already have some other code that does the download. – Wain Sep 05 '13 at 09:42

score 0 · Answer 2 · answered Sep 05 '13 at 09:51

Let iOS do the JSON parsing, then write it to a plain textfile through an outputstream

NSData *jsonData = yourData;
NSError *error;

// array of dictionary
NSArray *array = [NSJSONSerialization JSONObjectWithData:jsonData options:NSJSONReadingMutableLeaves error:&error];

if (error) {
    NSLog(@"Error: %@", error.localizedDescription);
} else {
    NSArray *documentsSearchPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [documentsSearchPaths count] == 0 ? nil : [documentsSearchPaths objectAtIndex:0];

    NSString *fileName = @"file.json";

    NSString *filePath = [documentsDirectory stringByAppendingPathComponent:fileName];

    NSOutputStream *outputStream = [NSOutputStream outputStreamToFileAtPath:filePath append:YES];
    [outputStream open];

    [NSJSONSerialization writeJSONObject:array
                                toStream:outputStream
                                 options:kNilOptions
                                   error:&error];
    [outputStream close];
}

How would I go about saving a JSON file from a webservice to a local JSON file?

2 Answers2

Linked